Vitamin A or retinol is a fat soluble vitamin that plays a vital role in healthy growth and development. The name retinol is because of the presence of this vitamin in the retina of eye.
Natural vitamin A occurs in the form of a mixture composed of various isomers, esters, acids, aldehydes and alcohols. Pure retinoic acid is a metabolite of vitamin A and is widely used for treating acne.
Natural sources of Vitamin A are animal sources such as liver and tissues. It can also be obtained from various plant sources like dark green and dark yellow vegetables. Other essential food sources of include cod liver oil, dairy products, eggs, carrots, tomatoes, papaya, melon, winter squash, spinach and cantaloupe.
Vision and Vitamin A always go hand in hand. Retinol present in the retina of the eye regulates the functioning of eyes. Human retina comprises of photo pigments known as rhodospin and iodospin that stores Vitamin A. Rhodospin comprises of rod cells that regulates visual excitation whereas iodospin play a vital role in regulating day vision. Deficiency of this vitamin leads to night blindness.
Apart from regulating the vision, Vitamin A is also essential for performing normal activities related to immune system, mental growth, tissue maintenance, bone development and various other physiological activities.
According to the RDA Vitamin A, children require 600-900 micrograms per day, adolescent require 900- 1,700 micrograms per day, adults require 3,333 IU per day and pregnant and lactating mothers require 4,333 IU per day.
Infants, kids, children and adults all are influenced by the optimum level of Vitamin A. Low intake of retinol will result in deficiency symptoms and high intake will cause toxicity. People suffering from Vitamin A deficiency show symptoms of weight loss, bone abnormalities, dry skin and growth retardation.
Overdose of this vitamin is predominant in people who consume liver of polar animals. Toxicity affects the individual in case of very high doses and intake. Common signs include blurred vision, bone pain, diarrhea, fatigue, headache, nausea, irritability, skin rashes, nausea, vomiting, hepatic fibrosis and pseudotumor.
So, it is very essential to maintain optimum level of Vitamin A in human body.